I have to build an aircrete wall and cavity against a brick party
wall. The party wall is 9" thick up to around 2 metres high, where it
changes into a single skin on the neighbours half of the party wall,
and next-doors ceiling joists fully penetrate this skin. I filled in
the gaps around these joists with foam when I demolished my old out-
house.
I intend to tie in a new wall that is 90 degrees from the party wall
using a wall starter system.
What I need to do is modify the upper section so it is effectively a
9" wall in order to properly isolate next door from the cavity. I
probably cannot chop out bricks from her wall in order to form a
standard bond with regular headers etc.

So what is the best way of tying in a new skin to to create a 9" wall
to the satisfaction of the BCO ? Bearing in mind that this new skin
will then further become one side of a cavity wall (i.e. it will be
tying in 2 directions).

Thanks,
Simon.